this one in the picture has 4 hd

Otherwise it is a beautiful product; I have been using it for 6 months and it works very well;

it is ready to use but without hd's; you have to buy these separately; it is ready to use but you only have to set the raid type according to the number of disks you have; you should follow the instructions of the nas programme;

if you buy it with one had you have no data retention security; if the hd goes, you've lost everything; if you buy it with two hds you have modest security; if one hd goes, you're at risk of losing data because you only have one hd until you replace the damaged one; for greater security you should buy it with 3-4 hds; mine has 4 hds

I bought it ready to use; you need ram if you want to install the nas operating system on ram; my IT cousin advised against it and told me to use the ready-made settings;